loading
Picture of How to Make a Spot Welder - for Cheap!!
 
Remove these adsRemove these ads by Signing Up

Step 1: You Might Be Surprised How Cheap It Can Be

Picture of You Might Be Surprised How Cheap It Can Be
1.jpg
2.jpg
Have you seen the video above?  If not, take a look now because it will help you as you go along in this instructable. 

A typical resistance Spot-Welder can range in price from about $200-$800, but with a little resourcefulness, and a bit of free time, you can make one like this for about $10 or less.

Spot welders are used to fuse thin sheets of metal together.  They are most likely used in the auto industry, as well as HVAC for welding metal ducting.  

There are a couple of videos you should see before starting on this project, because you may want some background on how the device works.

Here is how to: Make The Metal Melter

Here is what it can do:  The Metal Melter

Step 2: Take Some Measurements

Picture of Take Some Measurements
10.jpg
11.jpg
Measuring the base of my Metal Melter, I found it was about 4-1/4".

I found a 6' length of 1x6 common board for about $4, which actually measures out at 5-1/2", so it will work just fine.

Two pieces of the board will need to be cut to 12" lengths (5-1/2" x 12"), but the rest can be pushed through a table saw to trim the width down to 4-1/2" (1/4" wider than the transformer base).

Step 3: Roughing The Case Together

Picture of Roughing The Case Together
3.jpg
4.jpg
5.jpg
The piece of common board that you just trimmed down to 4-1/2" wide can be cut into 3 pieces measuring;

  4"  x  4-1/2"
12"  x  4-1/2"
24"  x  4-1/2"

The other 2 pieces of the common board should measure;

12" x 5-1/2" (x 2 pieces)

You'll also need 4 pieces of 2x2 measuring;

2" x 2" x 13-1/2" (x 2 pieces)

2" x 2" x 4" (x 2 pieces)

This is all the wood you'll need for building the casing.

I used a 3/4" rounding bit and my router to smooth the edges and give it a cleaner look.  

This is roughly how it will look when it's assembled.

Step 4: Prepping The Pieces

Picture of Prepping The Pieces
8.jpg
12.jpg
47.jpg
48.jpg
A notch needs to be cut on one of the 2x2 arms, and you'll see what this is for later on.  I found a piece of scrap can be used as a template. 

The notch can be cut out with a bandsaw, wood saw, or any other saw you can get creative with.  I used a jig-saw, but wouldn't recommend it as the safest option.

The back panel (4" x 4-1/2") also gets holes cut that will accommodate an electrical light switch, and a notch for a power cable.

The pieces get sanded, primed, and painted.  I chose to paint this black and yellow. 

Step 5: Additional Materials

Picture of Additional Materials
14.jpg
15.jpg
16.jpg
When I salvaged the Microwave Oven Transformer in this previous project , I saved some of the other components that can be used for our Spot Welder;

- The power cord
- The door handle
- Wires for the transformer terminals, with insulated spade connectors
- Power switch, with wires and insulated spade connectors

Aside from these, the only other items you'll need are;

- Simple light switch, with faceplate
- Copper offset terminal lugs that will hold  ( x 2)
- 1/4" hex screws( x 2)
- Small nails ( x 2)
- Length of solid copper wire (4AWG is better, but I used 6AWG in this project)

The solid copper wire can be snipped into 1" lengths, that fit nicely into the terminal lugs.  

The lugs have a mechanism that can be tightened with a screwdriver to secure the connection with the wire.  The tighter the better.

Step 6: Start Assembly

Picture of Start Assembly
18.jpg
19.jpg
Now that the wood is painted, finished, and dry (I gave it about 2 days), the unit can be assembled.

The back panel is for a light switch and a power cord.  

Before screwing the panel into the base, make sure your cord goes in first.  The thick piece at the end of the cord prevents it from pulling back though the hole.  

This is also the time to add the 2 pieces of 2" x 2" x 4" support blocks to the base.  Be sure of your measurements before you screw them down.  You want them to end up flush with the side panels when it's done.

The Metal Melter can be placed inside now, and when a good position is found, can be screwed to the base with a couple of small screws.

Now it's time to wire up the electrical system.

Step 7: The Electrical System

Picture of The Electrical System
21.jpg
22.jpg
23.jpg
25.jpg
26.jpg
Starting with the power cord coming into the casing, I stripped the black wire, and attached it to the bottom terminal of the light switch.

Next, I attached one of the wires I had salvaged, to the right terminal on the transformer, stripped the other end, and attached that to the top of the light switch.

The electrical could almost be finished here, but I wanted to add another switch, for safety and convenience, and that's where the salvaged switch from the microwave hack comes in.

The two wires attached to the switch can be wrapped with electrical tape to secure the connection and help insulate from electric shock.  

The both ends of the wires are stripped so the copper wire is exposed.

One wire connects to the left terminal of the Metal Melter's primary coil, and the other wire connects to the white wire on the power cable that runs back to the house.  

The electrical system is complete!

Step 8: Close It Up and Add The Arms

Picture of Close It Up and Add The Arms
28.jpg
29.jpg
30.jpg
31.jpg
34.jpg
The sides can be screwed on with 6 wood screws on each side.  I used 2" wood screws after drilling pilot holes to make sure the wood didn't split.

The trigger switch is attached near the tip of the top welder arm, and at a bit of an angle so it can be pressed easily.  I found that 2 small nails held this in place perfectly.  

Both arms can get inserted into the front of the casing, and with a bit of guesswork, a hole can be drilled through the side of the casing and into the end of the arms, so that when a nail is inserted, it will pivot.  

Now you can see why we needed the notch in the arm.

To help the arm stay in an upright position, I added a couple of screws and rubber bands to keep the tension.

This also provides a little back pressure, and stabilization when using the welder.  

Step 9: Adding The Electrodes

Picture of Adding The Electrodes
33.jpg
32.5.jpg
The copper lugs can be added to the tips of the arms.  

I drilled pilot holes with a 3/16th drill bit, then secured the lugs by pushing the hex bolts first through the hole in the lugs, then through the lugs on the the Metal Melter terminals.

One in the top, and one in the bottom.  It shouldn't matter which way they go, but I chose to make my top cable on the same side as the switch because it was easier to handle.

If the electrode tips don't line up perfectly, it's easy to bend them a little until they do.  

When finished, it should look like this.


Step 10: The Finished Result

Picture of The Finished Result
37.jpg
38.jpg
36.jpg
The Spot Welder is finished!

It will only work if the safety switch on the back is turned on, and even then, no power is delivered until the thumb operated switch is pressed.

To use, place thin sheets of metal between the electrode tips, then press the button with your thumb for about 3-4 seconds.

The massive electrical current pushing through the metal, heats it up to the point where it fuses with the other sheet.  

You can release your thumb from the switch and wait until the weld cools enough to handle.

Welding these metal washers worked so well, I couldn't break them by hand.  I had to use 2 pairs of pliers to get them to snap.  

When the energized electrode tips touch each-other, you can see the high-amp sparks.

Note: Burning galvanized metals may release zinc-oxide fumes.  Welding should be done in a well ventilated area.

Step 11: Additional Features

The electrode arms are only held in with nails, so if the nails are removed, the arms can be removed to extend the welders reach, and access difficult angles.

They go back together very easily, and the elastic can be conveniently replaced when necessary.

When the electrode tips are spent, it's easy to unscrew the bolt holding them in place, and add a fresh piece of copper wire.

Copper wire is relatively cheap.  You can get a pice of 12" 4AWG wire for about a dollar.  That means each tip is less than 10¢ each!

The power of the metal melter is still evident in the way this can bring iron metal to a boil!  Be careful running the welder too long because there is a chance the wires will get so hot that the insulation on the cables will start smoking and melt.

Now you know how to make my version of a cheap Spot Welder.  

If you haven't seen the step-by-step video, you can still see it here.

If you like this project, perhaps you'll like some of my others.  Check them out at www.thekingofrandom.com
1-40 of 192Next »
JeffG22 months ago

Thanks for this project. I managed to bodge one together and to my surprise it actually works - a bit TOO well actually. So, I have a couple of questions:

1) I am using 4 AWG THHN wire and it's very stiff. is there any way to connect thinner gauge wire to the thick leads? I want to make some sort of hand piece or probes to get into tighter spots (as opposed to having these fixed in one place and maneuvering the pieces to be welded under it). Leads to my next question…

2) The heat created is too intense and actually melts the metal too quickly (I am creating armatures out of relatively thin garment hanger wire). Is there any way to attach a dimmer switch/potentiometer to this? And if so, will a regular household dimmer switch work or do I need something else?

Any answers and suggestions are greatly appreciated.

kweixelman made it!2 months ago
I wired in the light and use pallet wood total if 15$ spent.
temp_-480450624.jpgtemp_1744139221.jpgtemp_1790108452.jpg

Looks awesome

harry.godwin38 months ago

Anyone noticed we're trying to fit 6 inches of 2x2 into a 4.5 inches of space?

2x2s are 1.5"x1.5"

vshljn059445 months ago

Sir can you please tell the rating of transformer you used in this project

that is the input and output voltage rating and current required to generate the melting at the desired spot to melt

pandamopeds136 months ago
Whatisthe thickest metal this will tolerate? Again, another fantastic write up sir.
Charles511 year ago

I put one of these contraptions together using your video as a guide and those of several others on YouTube. Melts wire amazingly. As an artist I need to spot weld wire together to form armatures. The wire gets red hot and will melt but it does not weld together and comes apart when additional pieces are added. Any idea why?

Sounds like too much resistance in the wire. Have you tried using bigger wire? Also keep the wire run from the transformer as short as possible.

Possum Living6 months ago

Great instructable, Grant!

RobertP76 months ago

Hi, enjoy seeing what you have made. On the spot welder what wire are you using leading to the welding tips? 2/0 seems too stiff to have the arms removable or did I just miss something here?

Thanks

Lots of projects I see I'm going to start doing in my retirement years!

fredF18 months ago

Are the transformer shunts left in or taken out?

The shunts are removed.

pnosko8 months ago

Let me ask a dumb question. You are using 1/4" hex screws to mount the terminal lugs to the arms. Considering that your metal melter videos show you melting similar screws, what is preventing these mounting screws from melting?

pnosko pnosko8 months ago

Answering my own question below after watching some educational electricity videos, I think the reason the 1/4" bolts are not affected is because the leads direct contact to the terminals make that the shortest path for the current, so it does not actually pass through the bolts.

Fission Chips9 months ago

Cool! I know this is dangerous to some extent, but exactly how dangerous is it?

felippec1 made it!10 months ago

I made it and work fine. thank you for inspiration.

Felippe Cardelino

Brasil

20140830_143453[1].jpg20140830_143519[1].jpg20140831_113731[1].jpg20140831_113738[1].jpg20140831_113744[1].jpg20140831_113750[1].jpg20140903_234133[1].jpg20140903_234153[1].jpg
SIRJAMES0911 months ago

Sir, you never cease to amze me!

this is just too cool!!! :)

TY for sharing Sir.

stamatelos1 year ago

Thank you it is very usuful i will try to bild sun

I_StarkGuy made it!1 year ago

Finished mine! I changed the design to adapt it to available materials and I added the microwave fan to cool the MOT.

Can you weld galvanized steel? Mine is not able to do it, though my math gives me above 950 amps.

100_7076.JPG100_7071.JPG

I think you can weld galvanized BUT the fumes given off are very toxic and potentially lethal. If you have to do this use a respirator, work outside or better yet, just try to avoid this if at all possible.

It is not that toxic in small quantities. And I work outside and I have been exposed to the fumes when melting screws.

The toxicity of galvanized metal when welded was one of the first lessons taught me by a pro. That said, just be careful (really, wear a respirator no matter where you are)!

JestGold1 year ago

Really like these projects and the metal melter/spot welder appear to be exactly what I need. Was wondering a couple of things:

a) I create metal sculptures from thin gauge wire rod and is there any way to regulate the amount of power so the metal fuses instead of melting (the spot welder seems to do just that)? and…

b) can the arms be separated or made into some sort of hand piece to make it more practical/accessible to the work?

Many thanks!

reddrexx1 year ago
I made one! But changed up the arms a bit. It works great.
14, 12:02 AM.jpg14, 12:02 AM.jpg
Are you sure you don't have AWG 2/0 wire ? It looks thicker than my AWG 2 wire. (2/0 is really 00 awg)
ccrow21 year ago
I have transformer from a die hard 6 and 12 volt battery charger I'm wondering how that would work, several input leads on the primary, the charger also had a 75 amp jump start setting also. Hmmm anybody wanna help me with where to start 6v 12v? I'd better do some math.
Pecheck1 year ago
late reply, but very awesome project. I'm definitely building one. I'll just ad a computer fan and some vent holes to by transformer housing.
kade1992 years ago
hey i was just wonder if for the MOT i should use the 2 AWG (since the 4 AWG melted) or if i should do the 8 gauge wire wrapped 16 times like in your arc welder video? which would be better overall for the spot welder?
Thanks!
I would think that if 8AWG wire wrapped 16 times worked better for the spot welder, then he probably would have said so, since they are both HIS videos ;-) But maybe he learned since making this one, and hasn't updated...
At any rate, 16 turns on the same core would result in higher voltage -- haven't watched the arc welder video yet -- guessing about 20V. Along with V increase, I (current, and resulting heat) goes down. I bet that the 2AWG (same number of turns) is the way to go here, since heating will occur in the secondary AND the work. I think the idea is to get the high current for the heat, and just make sure not to try melting anything that melts easier than the secondary's insulation! Assuming insulation was no issue, you'd simply have to keep the work easier to melt than the secondary itself, which is probably a complex relationship between relative masses and melting points.

But now I'm gonna have to go watch the arc welder video... are those capacitors I smell? :-)
GraphixS62 years ago
Do you know any place that you can reliably get dead microwaves. It seems my neighbors don't have a habit of just throwing them out.
f.masoni2 years ago
I love this project, i want to make one of my own but have a couple of questions.

Where i live the voltage of a power outlet is 220v does this change anything?

Also is it possible to make one that welds two separate spots at once with the same transformer.

Best Regards
calebwang2 years ago
I love your project. Your video editing is top notch as well.
The King of Random (author)  calebwang2 years ago
Thank you! Thank you!
Hi there. Thanks for this amazing project! I was amazed how easy it was to make. Luckily when I discovered this project, I knew were an old microwave was. I live in a small village in Guyana and most people here don't have microwaves. It was from a small restaurant. I successfully got the transformer out which was a little scary even for a 16 year old. I built a deluxe version of your design with the microwave light and fan incorporated in, along with four switches. My problem was that I didn't have any solid copper rod to use for the contacts. I had a few bronze welding rods so I used a small piece of that, instead. My welder is putting out about 1v. It melts nails and about anything else. I have not gotten it to actually weld. The metal to weld gets red hot but doesn't weld together. Any idea's whats wrong? I would appreciate any help. It's fun to melt metal, but it doesn't weld. Thanks.
Thanks for your comment! I'd love to see a little video of your welder as a video response to my video on YouTube, if you get a chance to do that?

It may help to press the contacts together harder when welding. You may also need more power. (Eg. Bigger transformer)
swolff12342 years ago
Yes, I am actually a ham. I got my license in Jan. No radio yet, but I have Echolink. I am getting my radio in March. Are you a ham? Thanks for all your help! BTW, the reply feature isn't working for me, I can only post new comments.
--
Sam Wolff KK4NVJ
The King of Random (author)  swolff12342 years ago
Awesome! I did get licensed but haven't ever done anything with it. I'm hoping that one day I can explore that world a little more :)
swolff12342 years ago
Found it! It was hiding from me..... Lol. Thanks again! Oh, how long does the trasformer last until the insulation on the 4 awg melts?
Best of luck,
Sam

--
Sam Wolff
KK4NVJ
The King of Random (author)  swolff12342 years ago
Hey, are you a Ham by chance?

If you use the transformer in short bursts of 10 seconds or less, you should be able to use it indefinitely. Allow time to cool in-between. You'll be able to tell the wires are starting to melt because they will be smoking. So stop when you see smoke (or before) and it should last forever.
1-40 of 192Next »